In the production of semiconductor elements, lithographic technique is applied in which a photoresist film is formed on a substrate such as silicon wafer, then exposed selectively with actinic radiation and developed whereby a resist pattern is formed on the substrate.
In recent years, pattern technology to form finer pattern by lithographic process has made a rapid progress in order to attain a higher degrees of integration in LSI. In forming finer patterns, various proposals have been made for exposure apparatuses, photoresists, anti-reflective coatings etc. in a wide variety of processes. For exposure apparatuses, processes using a shorter-wavelength light source effective for highly fine patterns, that is, processes using deep-ultraviolet rays such as KrF excimer laser (248 nm), ArF excimer laser (193 nm) etc., X-rays or electron beams have been proposed and some come to serve for practical use. In the lithographic process of using such short-wavelength light sources, highly sensitive chemically amplified resists corresponding to short-wavelength energy rays are proposed (Japanese Patent Application Laid-open Specification Nos. 209977/90, 19847/90, 206458/91, 211258/92, and 249682/93).
The process of using such a short-wavelength light source and chemically amplified resists is sensitively affected by acidic substances, basic substances and water present in an atmosphere. Therefore, there is the problem that if resists are allowed to stand for a long time after exposure until post exposure bake (PEB), pattern profiles after development become T-shaped (T top) in case of positive resists or post exposure delay (PED) takes place where the dimension of resist patterns varies depending on the length of time during the resists were left.
Further, if a short-wavelength and single-wavelength light source is used, incident light generally interferes with reflected light in the photoresist/substrate and photoresist/air interfaces, resulting in another problem (standing wave effect, multiple reflection effect) that the substantial magnitude of light exposure in the layer is altered to adversely affect resist patterns.
A method of forming an anti-reflective coating on a photoresist film (ARCOR method) has been proposed as one method for solving such PED and/or standing wave effect. Conventionally, a composition soluble in an organic solvent such as halogen-based solvent etc. has been proposed as a material for forming an anti-reflective coating in the ARCOR method. Recently a large number of processingly advantageous compositions soluble in resist developer solutions (aqueous alkaline solutions) have been proposed. However, compositions proposed heretofore are not adequate in the effect of solving the PED and/or standing wave effect, or even if these problems are solved, another new problem will occur.
For example, Japanese Patent Application Laid-open Specification No.188598/93 discloses a composition developable with aqueous developer, comprising a fluorocarbon compound, a water-soluble polymer binder and an amine. However if an anti-reflective coating made 6f this composition is formed on a resist film, an residue undeveloped (insolubilized layer) may be generated on the upper layer of the resulting resist pattern after development. This phenomenon occurs presumably because the surface of the resist film is made insoluble in a developer by the interaction between components in the anti-reflective coating and resist components such as novolak resin and naphthoquinone diazide in the presence of a quaternary ammonium salt in the developer. Further, the refractive index of the anti-reflective coating consisting of this composition developable with aqueous developer, comprising a fluorocarbon compound, a water-soluble polymer binder and an amine is far from an ideal refractive index.
Japanese Patent Application Laid-open Specification No.51523/94 discloses a composition comprising various water-soluble fluorine-containing compounds such as N-propyl-N-(2-hydroxyethyl) perfluorooctane sulfonamide etc. having a water solubility of 1% by weight or more, but the dimension stability of this composition when using short-wavelength light sources is hardly compatible with coating suitability for various resist materials and various stepped substrates.
Japanese Patent Application Laid-open Specification No. 118630/94 proposes a coating composition for chemically amplified resists, comprising a water-soluble film-forming component and a proton generating substance. The problem of this coating composition is that the problem of PED cannot be solved because its high refractive index makes the reflection preventing effect inadequate and a weak acid salt of ammonium exemplified as the proton generating substance inactivates an acid generated from the chemically amplified resist and present in the surface of the resist.
Japanese Patent Application Laid-open Specification No. 148896/94 discloses a composition comprising a water-soluble film-forming component and a fluorine-containing surface active agent, where a poly(vinyl pyrrolidone) homopolymer is mentioned as a preferable example of the water-soluble film-forming component and a fluorine-containing organic amnonium salt as a preferable example of the fluorine-containing surface active agent. Japanese Patent Application Laid-open Specification No.292562/96 discloses a composition containing a poly(vinyl pyrrolidone)-based resin, a fluorine-containing surface active agent, and a water-soluble fluorine compound of fluorinated aliphatic carboxylic acid amide such as 2-chloro-2,2-difluoroacetamide etc. However these compositions are poor in coating suitability for various resist materials and various substrates Ad- such as stepped substrates, so there are problems that resist materials to be applied or substrates as the object of coating are limited or a large amount of anti-reflective coating composition is required in applying the substrate. Further, these compositions cannot solve the problem of PED in the chemically amplified resist.
The present inventors previously found that an anti-reflective coating composition having low refractive index and being excellent in coating stability can be obtained by use of a composition comprising perfluoroalkylsulfonic acid, monoethanolamine, poly(vinyl pyrrolidone), a water-soluble alkyl siloxane polymer and water (Japanese Patent Application Laid-open Specification No. 291228/97), or by use of a combination of two or more fluorine compounds different in the length of the alkyl chain and a perfluoroalkyl group-containing sulfonyl amide compound (Japanese Patent Application Laid-open Specification No. 3001/98). However these compositions had the problem that coating defects in a streak form occur on stepped substrates such as logic IC etc.
Accordingly, the object of the present invention is to provide an anti-reflective coating composition free of the above problems and a method of forming a pattern by use thereof, that is, to provide an anti-reflective coating composition and a method of forming a pattern by use thereof where the composition is capable of solving the PED, standing wave effect and multiple reflection effect and has excellent suitability for applying on various resist materials and various substrates, specifically being applicable in a small amount of drip and having no coating defects even on stepped substrates.